docs: def find_seq_homologues(self, return_raw=False):
          """
          Uses NCBI BLAST to look for structures deposited in the PDB database
          that share __sequence__ homology with the target protein/chain.
          Bridges to Bio.BLAST.NCBIWWW.
          """
          
          
          # Get sequence from structure/chain
          # We could use Bio.PDB.Polypeptide?
          
          from Bio.SCOP.Raf import to_one_letter_code
          
          s = self
          seq_iter = s.get_residues()
          seq_str = ''
  
          for aa in seq_iter:
              if aa.resname in to_one_letter_code:
                  seq_str += to_one_letter_code[aa.resname]
          
          # Use BLAST to find homologous sequences with associated
          # structures in the PDB database.
          # Perhaps include local BLAST?
          
          from Bio.Blast.NCBIWWW import qblast
  
          # Adapt for short query sequences if needed
          # From http://www.ncbi.nlm.nih.gov/blast/producttable.shtml#shortp
          
          if len(seq_str) < 15:
              word_size = 2
              expect = 20000
              matrix_name = 'PAM30'
              filter = None
          else:
              word_size = 3
              expect = 10.0
              matrix_name = 'BLOSUM62'
              filter = 'SEG'
               
          query_result = qblast(  "blastp", "pdb", seq_str, 
                                  word_size, expect, matrix_name, filter)
          
          if return_raw:
             return query_result 
              
          # Parse BLAST result to yield results
          # PDBID : (E-Value, Identity, Positives, Gaps, Alignment)
          
          from Bio.Blast import NCBIXML
          
          blast_records = NCBIXML.read(query_result)
          
          results = []
          
          for alignment in blast_records.alignments:
              for hsps in alignment.hsps:
                  id_perc = "%s/%s" %(hsps.identities, alignment.length)
                  pos_perc = "%s/%s" %(hsps.positives, alignment.length)
                  gaps_perc = "%s/%s" %(hsps.gaps, alignment.length)
  
                  pdb_id = alignment.title.split('|')[3]
                  e_value = hsps.expect
                  
                  results.append( ( pdb_id,
                                  "%2.5e" %e_value,
                                  id_perc, 
                                  pos_perc, 
                                  gaps_perc,
                                  '\n'.join([hsps.query, hsps.match, hsps.sbjct]) ) )
  
          return results